Pilocytic astrocytomas (PA) are benign CNS tumors with high 5- and 10-year survival rates. Data on aggressive course of PA have occurred since the late 20th century. The purpose of this study was to summarize data on patients with aggressive course of PA. We analyzed own patients with conventional PA, PA with aggressive clinical course and literature data on HGAP. Aggressive group is highly heterogeneous without significant differences in anatomical location between groups. Patients with aggressive course and HGAP were older (M=41, 45.5, and 34 years). Overall 5-year survival in patients aggressive PA was 45%, while no deaths were recorded in the group of conventional PAs. Signs of anaplasia according to histological data and Ki-67 index >8 distinguish conventional PA and tumors with aggressive course. Next-generation sequencing and methylation profiling will improve detection of HGAP.